1. Field of the Invention
The present invention relates to a video tape recorder (VTR) which allows preset program recording, and more particularly to a video tape recorder which allows preset program recording by the VPT (Video Programming by TELETEXT) system by inputting program preset codes such as "G-code".
2. Description of the Background Art
Timer program recording is the most popular recording system using a VTR. In timer program recording, a user sets in advance the channel, date, time and the like of a desired program to be subsequently broadcast, and recording is conducted automatically based on the preset data. However, when the broadcast time of the program is advanced, deferred, or postponed by the TV station, the desired program cannot be recorded appropriately.
In order to solve such a problem, the VPT system has been employed in Europe. Lately, TV broadcasting employs the teletext system utilizing a vertical blanking period. The details of the teletext technology is disclosed in U.S. Pat. No. 3,982,065.
FIG. 8 shows an example of the TV program list transmitted as one of teletext services. The program list includes a date 2, time 3, a program identifying code 4, and a title 5 of every program to be broadcast within, for example, a week by a TV station 1. Program identifying code 4 is multiplexed on a video signal of the program during broadcasting to distinguish the program from other programs.
In Germany, for example, a VPS (Video Program System) code is transmitted as the program identifying code. The VPS code is multiplexed on the sixteenth horizontal data line in the first field of a video signal.
In United Kingdom, a PDC (Program Delivery Control) code is transmitted as the program identifying code. The PDC code is multiplexed on the 7th through 22nd horizontal data lines in the first field of the video signal and on the 320th through 335th horizontal data lines in the second field of the video signal.
In the United States, an EDS (Extended Data Service) code is transmitted as the program identifying code. The EDS code is multiplexed on the 21st horizontal data line in the second field of the video signal.
The VPT system utilizes the above-mentioned program list for preset program recording. The details of the VPT system is disclosed, for example, in DE3335082C2.
When preset program recording is conducted by the VPT system, a program list is transmitted from a broadcasting station and displayed on the display screen. A user examines the program list and selects a desired program by moving a cursor and the like, whereby necessary data for preset program recording are taken in the VTR and decoded.
When the decoded preset data include the program identifying code such as VPS code, PDC code or EDS code, recording is preferentially conducted based on the program identifying code. More particularly, when the time draws near to the scheduled broadcast time of the preset program, a program identifying code which has been transmitted from the broadcasting station of the program is received, and the program identifying code is compared with the program identifying code which has been already set. Recording starts when those codes coincide with each other, and recording continues until the program identifying code transmitted from the broadcasting station disappears, or until it comes to be non-coincident with the set program identifying code. Therefore, even when the broadcast time of the program is changed by the broadcasting station, the program can be recorded accordingly.
The program identifying code which is transmitted from the broadcasting station is monitored continuously from 8:00 pm the previous day to 4:00 am the next day of the scheduled broadcast date of the preset program, for example. The time period in which the program identifying code is monitored is called the valid period. The program identifying code included in the program list is valid only during the valid period corresponding to a particular program.
When the decoded preset data does not include a program identifying code, the normal timer reservation mode is set, so that recording is conducted based on the set starting and the ending broadcast times. More particularly, the current time is compared with the set starting broadcast time, and recording starts when those times coincide with each other, while recording is completed when the current time coincides with the set ending broadcast time. The related technology is disclosed in European Patent No. 0255108B1.
Meanwhile, the program preset system called "VCR.cndot.PLUS" has been utilized recently in Europe which allows simplified operation of timer program recording. According to the VCR.cndot.PLUS system, the preset data such as the broadcasting station, date and time of a program are compressed mathematically, and converted into a program preset code having eight digits called a "G-code". Such program preset codes are allotted to respective programs and printed on newspapers and magazines. The "G-code" is input to VTR by a user and decoded into preset data including the name of broadcasting station, date and time. Thus, the normal timer preset mode is set, whereby recording is controlled based on the preset data. More particularly, the current time is compared with the decoded starting broadcast time, and recording starts when those coincide with each other. When the current time and the decoded ending broadcast time coincide with each other, recording is completed.
As described above, the VPT system is superior to the VCR.cndot.PLUS system in that a desired program can be always recorded more appropriately. Therefore, a user normally selects preset program recording by the VPT system.
When setting the preset data by the VPT system, it is necessary to receive the teletext data and reproduce the program list. Since the teletext data are multiplexed on the video signals in the vertical blanking period, it normally takes several tens of seconds to acquire all the data. Therefore, preset operation by the VPT system is time consuming. On the other hand, preset operation by the VCR.cndot.PLUS system is very simple, as it requires the input of the "G-code" only.
In this respect, the preset data are often set by the VCR.cndot.PLUS system even for a program having a program identifying code. In this case, if broadcast time of the program is advanced, deferred or postponed by the broadcasting station, recording is not properly conducted accordingly even though the program identifying code is allotted to the preset program. Consequently, sometimes the beginning or the ending of the preset program is not recorded, or the program which is totally different from the preset program is recorded.
Generally, every broadcasting station transmits the program list covering only one week, so that preset program recording by the VPT system is not possible for such a program that is to be broadcast at a time more than one week later. Meanwhile, "G-codes" for the programs to be broadcasted at a time more than one week later are printed on a magazine and the like. Therefore, the VCR.cndot.PLUS system has been the only way for presetting recording of the program which is broadcast sometime more than one week later. Consequently, if the broadcast time of the program is changed by the broadcasting station, the program cannot be recorded appropriately.